The transmission of electrical power from electric generator to residential areas involves a combination of transmission devices which make up a transmission system. The present application is concerned with a distribution substation of the type used to step the voltage down from the transmission voltage to a distribution voltage of 5 to 35 KV. A distribution substation of the type contemplated herein is shown in U.S. Pat. No. 4,360,849 which issued on Nov. 23, 1982 and is assigned to the assignee of the present application.
In the power distribution system disclosed in the above patent, a distribution substation is described which was designed to reduce the total costs, such as labor, equipment and land, at the power distribution level. This type of substation was designed to eliminate the conventional practice of providing the required components from a variety of sources, assemble and test those components at the substation site. This often resulted in a construction time table that was dependent upon the time required to deliver the last component. As an example, the transformer could take 26 weeks whereas the switchgear could take 40 to 50 weeks or vice versa resulting in a holding time of up to a half year of the parts received at the earlier date.
The power distribution system contemplated a prepackaged substation made up of independent modules which could be assembled at the point of manufacture, tested, disassembled, shipped to the customer site, and readily assembled at the substation site. All the components which make up the substation were engineered, selected, assembled and tested in the system by a single manufacturer. This system included the transformer, primary circuit breakers, low voltage switchgear, relays, meters, lightning arresters and all other required hardware accessories. The system was fully tested at the point of manufacture and retested after assembly at the site. Land costs were reduced since a single pad mount and a support pad were all that was required to accommodate the transformer and feeder modules.